The invention relates to the field of antiviral therapy and, in particular, to non-nucleoside compounds that inhibit HIV reverse transcriptase and are useful for treating Human Immunodeficiency Virus (HIV) mediated diseases. The invention provides novel heterocyclic compounds according to formula I, for treatment or prophylaxis of HIV mediated diseases, AIDS or ARC, employing said compounds in monotherapy or in combination therapy.
The human immunodeficiency virus HIV is the causative agent of acquired immunodeficiency syndrome (AIDS), a disease characterized by the destruction of the immune system, particularly of the CD4+ T-cell, with attendant susceptibility to opportunistic infections. HIV infection is also associated with a precursor AIDS-related complex (ARC), a syndrome characterized by symptoms such as persistent generalized lymphadenopathy, fever and weight loss.
In common with other retroviruses, the HIV genome encodes protein precursors known as gag and gag-pol which are processed by the viral protease to afford the protease, reverse transcriptase (RT), endonuclease/integrase and mature structural proteins of the virus core. Interruption of this processing prevents the production of normally infectious virus. Considerable efforts have been directed towards the control of HIV by inhibition of virally encoded enzymes.
Two enzyme have been extensively studied for HIV-1 chemotherapy: HIV protease and HIV reverse transcriptase. (J. S. G. Montaner et al., Antiretroviral therapy: ‘the state of the art’, Biomed & Pharmacother. 1999 53:63-72; R. W. Shafer and D. A. Vuitton, Highly active retroviral therapy (HAART) for the treatment of infection with human immunodeficiency virus type, Biomed. & Pharmacother. 1999 53: 73-86; E. De Clercq, New Developments in Anti-HIV Chemotherap. Curr. Med. Chem. 2001 8:1543-1572). Two general classes of RTI inhibitors have been identified: nucleoside reverse transcriptase inhibitors (NRTI) and non-nucleoside reverse transcriptase inhibitors. Currently the CCR5 co-receptor has emerged as a potential target for anti-HIV chemotherapy (D. Chantry, Expert Opin. Emerg Drugs 2004 9(1):1-7; C. G. Barber, Curr. Opin. Invest. Drugs 2004 5(8):851-861; D. Schols, Curr. Topics Med. Chem. 2004 4(9):883-893; N. A. Meanwell and J. F. Kadow, Curr. Opin. Drug Discov. Dev. 2003 6(4):451-461). Drugs targeted at new enzymatic targets have entered the market including integrase inhibitors typified by Raltegravir (Merck) has been approved by the FDA and Elvitegravir (Gilead Sciences and Japan Tobacco) is in phase II trials. The CCR5 antagonist maraviroc (SELZENTRY™, Pfizer) has also been approved by the FDA for anti-HIV-1 therapy.
NRTIs typically are 2′,3′-dideoxynucleoside (ddN) analogs which must be phosphorylated prior to interacting with viral RT. The corresponding triphosphates function as competitive inhibitors or alternative substrates for viral RT. After incorporation into nucleic acids the nucleoside analogs terminate the chain elongation process. HIV reverse transcriptase has DNA editing capabilities which enable resistant strains to overcome the blockade by cleaving the nucleoside analog and continuing the elongation. Currently clinically used NRTIs include zidovudine (AZT), didanosine (ddI), zalcitabine (ddC), stavudine (d4T), lamivudine (3TC) and tenofovir (PMPA).
NNRTIs were first discovered in 1989. NNRTI are allosteric inhibitors which bind reversibly at a nonsubstrate-binding site on the HIV reverse transcriptase thereby altering the shape of the active site or blocking polymerase activity (R. W. Buckheit, Jr., Non-nucleoside reverse transcriptase inhibitors: perspectives for novel therapeutic compounds and strategies for treatment of HIV infection, Expert Opin. Investig. Drugs 2001 10(8)1423-1442; E. De Clercq, The role of non-nucleoside reverse transcriptase inhibitors (NNRTIs) in the therapy of HIV infection, Antiviral Res. 1998 38:153-179; E. De Clercq, New Developments in Anti-HIV Chemotherapy, Current Med. Chem. 2001 8(13):1543-1572; G. Moyle, The Emerging Roles of Non-Nucleoside Reverse Transcriptase Inhibitors in Antiviral Therapy, Drugs 2001 61 (1): 19-26). Although over thirty structural classes of NNRTIs have been identified in the laboratory, only three compounds have been approved for HIV therapy: efavirenz, nevirapine and delavirdine.
Initially viewed as a promising class of compounds, in vitro and in vivo studies quickly revealed the NNRTIs presented a low barrier to the emergence of drug resistant HIV strains and class-specific toxicity. Drug resistance frequently develops with only a single point mutation in the RT. While combination therapy with NRTIs, PIs and NNRTIs has, in many cases, dramatically lowered viral loads and slowed disease progression, significant therapeutic problems remain. (R. M. Gulick, Eur. Soc. Clin. Microbiol. and Inf. Dis. 2003 9(3): 186-193) The cocktails are not effective in all patients, potentially severe adverse reactions often occur and the rapidly reproducing HIV virus has proven adroit at creating mutant drug-resistant variants of wild type protease and reverse transcriptase. There remains a need for safer drugs with activity against wild type and commonly occurring resistant strains of HIV.
Pyridazinone non-nucleoside reverse transcriptase inhibitors have been described by J. P. Dunn et al. in U.S. Pat. No. 7,189,718 issued Mar. 13, 2007 and by J. P. Dunn et al. in U.S. Publication No. 2005021554 filed Mar. 22, 2005. 5-Aralkyl-2,4-dihydro-[1,2,4]triazol-3-one, 5-aralkyl-3H-[1,3,4]oxadiazol-2-one and 5-aralkyl-3H-[1,3,4]thiadiazol-2-one non-nucleoside reverse transcriptase inhibitors have been disclosed by J. P. Dunn et al. in U.S. Pat. No. 7,208,059 issued Apr. 24, 2007, U.S. Patent Publication 20060225874 published Oct. 5, 2006 and U.S. Publication No. 20060025462 filed Jun. 27, 2005. Related compounds are disclosed by Y. D. Saito et al. in U.S. Publication No. 20070078128 published Apr. 5, 2007. Phenylacetamide non-nucleoside reverse transcriptase inhibitors have been disclosed by J. P. Dunn et al. in U.S. Pat. No. 7,166,738 issued Jan. 23, 2007 and methods for treating retroviral infection with phenylacetamide compounds have been disclosed by J. P. Dunn et al. in U.S. Publication No. 20050239880 published Oct. 27, 2005; T. Mirzadegan and T. Silva in U.S. Publication No. 20070088053 published Apr. 19, 2007; and by Z. K. Sweeney and T. Silva in U.S. Publication No. 20070088015 published Apr. 19, 2007. These applications are hereby incorporated by reference in their entirety.
In WO2006/067587 published Jun. 26, 2006, L. H. Jones et al. disclose phenoxyacetamide derivatives and compositions containing them which bind HIV-1 reverse transcriptase and are modulators, especially inhibitors, thereof. K. R. Romines et al (J. Med. Chem. 2006 49(2):727-739) and P. Bonneau et al. (U.S. Publication No. 20060069261 published Mar. 30, 2006) describe phenoxyacetamides that inhibit HIV-1 reverse transcriptase. In U.S. Patent Publication 2007/0021442 published Jan. 25, 2007, S. A. Saggar et al. disclose diphenyl ether HIV-1 reverse transcriptase inhibitors.